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ISWEC

The Inertial Sea Wave Energy Converter is our floating system that produces electricity from wave energy, in turn powering off-shore plants.

Technology

Wave energy is seen to be the largest unused source of renewable energy on the planet: ENEA and RSE have calculated that if this could be fully harnessed, we could obtain 80 thousand billion kWh of energy: five times the annual electricity demand of the whole world. Our ISWEC system does exactly that: it converts the energy of ocean waves into electrical energy, making this immediately available for off-shore plants or feeding it directly into the electricity grid to provide power to coastal communities. The full name of this system is the Inertial Sea Wave Energy Converter , and we developed it in collaboration with Wave for Energy S.r.l, a spin-off of the Politecnico di Torino. The system consists of a sealed floating hull containing a pair of gyroscopic systems , connected to two generators. The waves cause the unit to pitch; it is anchored to the ocean floor, but free to move and oscillate. This pitching movement is intercepted by the two gyroscopic systems which are connected to the generators, and these in turn transform this movement into electrical energy. A simple solution, with cutting-edge technology at its heart.

Context

ISWEC is perfect for supplying electricity to off-shore plants, and to Oil & Gas platforms in particular. The first pilot plant is already active in Ravenna, and is connected to our PC80 platform and integrated with a photovoltaic system. This type of application increases the energy self-sufficiency of offshore structures that are located away from the coast, and perhaps in geographical contexts where an electricity supply cannot be taken for granted. This first version has succeeded in producing 105% of its nominal power of 50 kW, but we are currently working on an industrial model that will be able to reach a peak of 100 kW; the launch is scheduled for 2020. A machine of this type will deliver energy to medium-large plants, and will represent a major step forward in terms of the sustainability of these.

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Offshore life - On the Garibaldi C | ENi Video Channel

Technological challenge

Wave energy is the most constant of all renewable energy types: unlike the sun and the wind, the sea never stays still. In addition, it is also the most "dense", as it consists of nothing more than the concentration of energy produced by the wind, which in turn concentrates the energy produced by the heating of the atmosphere (by the sun). The average energy power obtainable from waves is around 2-3 kW per square metre, four to five times that of wind power and up to twenty times that of photovoltaics. During the development of this technology, we encountered two major issues: corrosion due to the salt in the water, and variations in wave intensity. We succeeded in resolving both of these with ISWEC - first and foremost, the delicate and moving parts are inside the sealed hull, and as such, completely isolated from the salt water, and secondly, the gyroscopic systems that feed the two generators are automatically calibrated in order to respond to varying weather and sea conditions. ISWEC converts wave motion into electricity with an inertial system based on the law of conservation of angular momentum: The waves cause the hull to pitch and this pitching movement is intercepted by a gyroscope rotating on an axis perpendicular to that of pitch, which in turn rotates a second gyroscope perpendicular to both and this transforms the movement into electricity. ISWEC has an added advantage in the energy capture process, the rotation speed of gyroscopic system can be calibrated to optimise the hull's inertial response to the length of local waves; this feature, implemented by Eni for the first time in the world on an industrial prototype, is the real difference between this system and other capture systems. It is possible to vary the device's inertia in the same way as if we had changed its size, making it a virtual variable geometry system. The two gyroscopes rotate on an axis that is perpendicular to the pitching of the hull, whilst simultaneously oscillating on a third axis, which is perpendicular to both. The movement of the waves is thus amplified in accordance with the principle of conservation of angular momentum of the gyroscopes, and transmitted to the electric generators. 

 

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ISWEC - The energy that comes from the sea | Eni Video Channel

Industrial integration

ISWEC is an example of the teamwork that lies behind all of our proprietary technology. In this instance, one of the most complex technological challenges to be overcome was the calibration of the gyroscopic system in order to optimise the response of the latter to local sea conditions. This was a fundamental step in taking full advantage of the constant availability that is the most significant feature of wave energy. Here, the task was to analyse and cross-reference large amounts of data from different sources, both meteorological data and information relating to the operation of the machine. HPC4 and HPC5, our supercomputers, provided the assistance we needed: thanks to their computing power, we use advanced mathematical models to develop answer formulas suited to every situation. And so today, the "Cradle of Energy" never stops, guaranteeing constant production levels.

Wave energy is the largest untapped renewable energy source. Highly predictable with low variability and high energy density, it is the renewable source closet to fossil fuels in terms of advantages, making it particularly promising for the decarbonization of offshore O&G activities

by ANDREA ALESSI, R&D PROJECT MANAGER FOR MARINE ENERGY

Environmental impact

Although different from one another in many ways, all coastal towns and villages share similar characteristics, as they have similar needs. A small inhabited island is not so different from an Oil & Gas platform: their horizons and the challenge posed by distance are the same for both.  For this reason, we are assessing the various possible applications of ISWEC for the supply of electricity to communities on small islands. By combining multiple devices, we could create marine energy parks with enough power to guarantee an electricity supply to island villages. This goal could be achieved when the industrial versions of ISWEC, which we are currently developing with the Cassa Depositi e Prestiti, Fincantieri and Terna, become available.